Rigid recording disk cartridges having a circular, floppy magnetic or optical disk rotatably mounted within the disk cartridge case are well known. The cartridge is mountable on a disk drive apparatus to rotate the recording disk and access the disk by a recording head for recording or reproducing information. The disk cartridge includes a rotatable magnetic or optical disk, a cartridge case for housing the disk having a central axis and a front wall, and a U-shaped shutter which slides on the front wall of the case.
Referring to FIGS. 1 and 2, a cartridge 10' includes generally rectangular upper and lower walls 12 which mate to form the outer dimensions of the cartridge case 14. A drive shaft opening is formed through a central portion of the lower wall 12 to receive a drive shaft to rotate the magnetic disk 16 within the cartridge case 14. A head access opening is formed in both the upper and lower walls 12 between the central axis and the front wall 20 to access the magnetic disk 16. The head access opening is opened and closed by the shutter 130 which slides between open and closed positions in a sliding surface 26 which is defined by parallel edges 28. A spring biases the shutter 130 in the closed position to cover and close the head access openings. When the cartridge 10' is inserted into the disk drive, the shutter 130 is moved to the open position by the disk drive to provide access to the disk 16.
The current shutter design for disk cartridges also includes two tabs 144 which engage and ride in an elongate slot 46 in one wall 12 of the cartridge 10' to secure and guide the shutter 130 on the cartridge case 14. This is shown in FIG. 1. This performs satisfactorily but still leaves room for improvement. The tabs 144 are formed with a punch press. During fabrication, the tabs 144 have a raised surface which scratches adjacent shutters 130 during shipping. In the packaged finished disk cartridge, this raised surface abrades the shutter printing. Additionally, there is a 5.degree. to 10.degree. angle between the shutter 130 and the front wall 20 of the cartridge 10'. This angle contributes to decreased shutter horizontal drop performance. Such shutter displacement frequently results from the cartridge 10' being dropped during handling. One edge 40 of the shutter 130 rides over the edge 28 to encompass the thicker portion of the case 14. This can prevent the shutter 130 from opening upon insertion into the disk drive or prevent the cartridge 10' from loading into the drive.
In a modification of this design, the tabs are formed on the opposite side of the punched hole to help prevent the shutter from failing during a horizontal shutter drop. However, this shutter suffers from the same disadvantages as the conventional punched shutters.